A North Wales Police spokesman said the collision involved a Land Rover towing a caravan, which was in a collision with a Renault Clio. The road stayed partly shut until after 3pm.

One eye-witness, from Caernarfon, said: “It looks very serious. There’s a caravan that’s landed on its side, and a car that’s ended up on its roof and another car looks smashed up.”

Another passenger, who lives in Colwyn Bay said: “One of them was a silver car but we couldn’t see properly. The fire service and police have just got here. I saw a man with blood on his face walking into an ambulance.”

The closure led to a flurry of messages as frustrated drivers sat in queues. Karina Galli tweeted: “Traffic at a standstill on A55 up to Abergele! Avoid the road!”

As the traffic east-bound was building up , vehicles were diverted along the A547 to Llanddulas and Abergele.

Traffic Wales said one lane was closed and queuing traffic on A55 eastbound because of the accident. It reported the build up of vehicles was caused by the collision and recovery vehicles having to move the vehicles from the road. It added the congestion stretched several miles to the promenade at Old Colwyn.

Later, police and Traffic Wales were able to open one of the eastbound lanes.

A North Wales Fire and Rescue spokeswoman said: “We sent two crews from Abergele and Colwyn Bay to the scene but nobody was trapped. One person was treated by ambulance paramedics at the scene. Our fire officers attended to the two vehicles and made them safe and we then left the scene.”

A North Wales Ambulance spokesman said: “Three casualties were taken to Ysbyty Glan Clwyd, Bodelwyddan accident and emergency unit with minor injuries.”

A North Wales Police spokesman said emergency services and highways staff had worked swiftly and efficiently together to deal with the collision. One lane was reopened within an hour of the accident and both lanes were opened by 3.10pm. Police are appealing for witnesses.